This invention relates to sheet registering devices and, particularly, to a mechanism for registering sheets in a printing machine or the like which includes a conveyor board for delivering the sheets seriatim to the registering mechanism.
The production of high quality copies on office-type printing machines, such as lithographic duplicating machines, depends to a large extent on the ability of the machine to deliver sheets to a printing couple of the machine in accurate registration. Generally, registration of the sheets is effected on the conveyor board immediately prior to feeding the sheets to the printing couple. Sheet guides, normally including a fixed stop guide at one side of the conveyor board and a pusher or jogger guide at the opposite side of the conveyor board, conventionally are disposed immediately prior to advancement of the sheet to the printing couple. The jogger guide acts against a side edge of a sheet to move the sheet laterally to engage an opposite side edge of the sheet against the stop guide.
In conventional machines, the side guides on the conveyor board are positioned to align the sheets fed from a sheet tray to an image on a printing plate or a master mounted on a master cylinder of the printing couple. A sheet is advanced from the feed tray to the conveyor board, arrested momentarily between the side guides with a lead end of the sheet in contact with stop fingers on an impression cylinder and then jogged by the jogger guide against the stop guide to register the sheet prior to forwarding the sheet to the printing couple.
A common form of registering mechanism of the prior art includes a rigid jogger guide for jogging the sheet against a stop guide which is provided with spring means such as leaf spring members which abut against a side edge of the sheet. The leaf spring members are provided to yield and thereby compensate for variations in the squareness of the sheets to effect proper registration.
In particular, most paper stock is not cut perfectly square and the sheets vary in squareness and width from ream-to-ream. Consequently, one of the problems of prior art sheet registering mechanisms is their inability to adequately compensate for sheets which are skewed in orientation or out-of-square in cut. This is particularly true in machines which print or duplicate various kinds of sheets at high speed.
In addition to the lack of squareness of the sheets, other variations affecting registration are caused by wearing of parts of the registering devices, such as bushings, cams and shafts associated with the register system and the inability of the registering springs, such as the aforesaid leaf spring members, to adjust accordingly.
Heretofore, there has been no adequate means for adjusting the biasing pressure of the spring means of the registering device to accommodate sheets of varying squareness and width.
Another problem of prior art registering mechanisms is their inability to be readily changed or repositioned to accommodate changes in sheet size, weight or the like. With known prior art mechanisms, such procedures are quite time consuming and require considerable manual dexterity on the part of the machine operator.
Still another problem with art devices of the character described is their inability to be readily changed to position the jogger guide at either side of the conveyor board without considerable time consuming manipulation. In particular, when various printing or duplicating jobs are required to print images on both the front and back of a sheet, it is desirable to reverse the position of the jogger and stop guides at either side of the conveyor board. These types of printing jobs commonly are termed "work and turn" jobs, and usually are encountered with duplicating forms requiring precise line orientation. In most prior art machines, the stop guide and the jogger guide must be completely removed from the conveyor board to have their positions reversed on opposite sides of the board to jog the sheets in opposite directions for printing jobs of the character described.
The present invention is directed to solving problems described above in known sheet registering mechanisms by providing a jogger side guide with a sensitive spring loaded blade for jogging a sheet against a stop side guide, and selectively settable calibrated dial means for adjusting the spring pressure of the blade means in minute increments to effect precise registration of the sheets at high speed on the conveyor board of a printing or duplicating machine. The dial means is interchangeable for varying the calibration, and the spring loaded blade means is provided with floating movement to accommodate sheets which are skewed in orientation or out-of-square in cut. The side guides also can be converted from a stop guide to a jogger guide without removing the guides from their respective positions on opposite sides of the conveyor board.